How do you use chmod with the -R option and what are symbolic permission shortcuts?

-R walks a directory tree and applies the change to everything inside; bare operators like +x / -w / =r default to "all" (same as a+x) when you omit the who.

A real trap with recursive numeric modes: chmod -R 755 forces the execute bit onto files too, not just directories. Often you want execute on directories (to enter them) but not on data files. The symbolic capital-X helps here — chmod -R a+rX dir/ adds execute only to directories and to files that already had some execute bit, leaving plain data files alone.

Recursive permission change:

chmod -R 755 directory/    # Apply to directory and all contents

Symbolic shortcuts:

Combining changes:

chmod u+rwx,g+rx,o-rwx file    # Multiple changes at once
chmod u=rwx,g=rx,o= file       # Set exact permissions

Permission calculation:

rwx = 4+2+1 = 7
r-x = 4+0+1 = 5
r-- = 4+0+0 = 4


**Go deeper:**

- ![doc](/quizzes/_icons/doc.svg) [chmod(1) — modes, including capital `X`](https://man7.org/linux/man-pages/man1/chmod.1.html) — the `X` (conditional execute) trick for recursive directory-vs-file safety.